In very numerous technical fields, it is necessary to control the working operations of several machines, these machines being either of the same type or of different types, and each machine being intended to execute operations different from each other. Such is the case, for instance, in the audio-visual industry, when several slide projectors must be controlled to execute an audio-visual program during which each slide projector is controlled on analogy with one or several other projectors or in a different manner.
Effectively, one can imagine that in an audio-visual program, two projectors are coupled on a same zone of a screen to project, in succession, mixing views on this same zone, while other projectors project, on other zones of the same screen, other views that can be eventually occulted; a present program can then be repeated identically, any number of times.
In another technical field, machine tools as for instance lathes, milling machines or other machines should also be controlled in function of a given work that can be reproduced to manufacture various articles. The same is true for other types of machines, such as stamping machines, welding machines, cutting, folding machines etc.
Until now, devices are known, for instance the so-called numerical control devices that permit controlling a sequence of operations on a same machine and possibly a sequence of operations interesting several machines. However, these devices are very complex and require parallel links between the actual numerical control element and the various machines to be controlled or the different parts of machines to be controlled. This method thus lead to use a great number of conductors and a given device can only be used with the machine or the groups of machines for which it has been designed.